1. Field of the Invention
The present invention relates generally to a vane-type rotary compressor which can be suitably used in an automotive air conditioner system and so forth. More specifically, the invention relates to production of a vane-type rotary compressor.
2. Description of the Background Art
In general, a vane-type rotary compressor has a rotor carrying a plurality of rotor vanes which are disposed in the rotor for radial movement toward and away with respect to vane receptacles formed in the rotor body. The rotor is received within a cam ring in rotatable fashion. Both axial ends of the cam ring are closed by means of a front and side plates. The cam ring, the rotor with the vanes, the front and side plates forms a rotor assembly. The rotor assembly is housed within a housing.
The cam ring defines a oval or elliptic rotor receptacle opening to receive therein the rotor. The rotor vanes radially movably disposed within the vane receptacles move to maintain sliding contact with the inner periphery of the opening. With this construction, a plurality of mutually separated working chambers are defined between the adjacent rotor vanes. During one cycle of rotation, each working chamber is subject to expansion of volume and compression of volume. In the rotational angular range in which the volume of working chamber is increased, a working fluid is drawn and introduced into the working chamber. On the other hand, the rotational angular range, in which the volume of the working chamber is decreased, a working fluid in the working chamber is compressed and discharged from the working chamber.
In the recent years, requirement for lighter weight compressor becomes stronger. In order to answer such requirement. Japanese Utility Model First (unexamined) Publication (Jikkai) Showa 59-27101 discloses a vane-type compressor which comprises a rotor, side plate, cam ring and so forth made of aluminium or aluminium alloy. An aluminium or aluminium alloy is a useful material for reducing the weight of the compressor. On the other hand, such materials may encounter other problems because of relative great linear expansion coefficient. In case that the aluminium material is used for forming the side plate, contact pressure between a periphery of a boss section and ball or needle bearing changes according to rising of temperature during compressor operation.
In general, the bearing is disposed in the boss section with contracting the inner diameter thereof. A clearance between the periphery of the boss section and the bearing is set with respect to the contracted diameter upon assembling under normal temperature. As will be appreciated, since the linear expansion coefficient of the aluminium side plate is greater than the bearing which is made of steel, contacting pressure between the engaging surfaces of the boss section of the aluminium side plate and the bearing can be decreased according to rising of the temperature. This expands clearance between the bearing and the rotor shaft. Expansion of clearance may particularly affect unbalanced vane-type compressor, such as five vane-type compressor. Namely, in such unbalanced-type compressors, the rotor shaft tends to be driven by its axis offset from the center. The offset of the rotor shaft tends to create noise and/or vibration. Also, offset of the rotor shaft axis can cause baking in between mating surfaces of the cam ring and the rotor to degrade durability.